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compiler: allow larger-than-int values to be sent across a channel

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Instead of storing the value to send/receive in the coroutine promise,
store only a pointer in the promise. This simplifies the code a lot and
allows larger value sizes to be sent across a channel.

Unfortunately, this new system has a code size impact. For example,
compiling testdata/channel.go for the BBC micro:bit, there is an
increase in code size from 4776 bytes to 4856 bytes. However, the
improved flexibility and simplicity of the code should be worth it. If
this becomes an issue, we can always refactor the code at a later time.
This commit is contained in:
Ayke van Laethem
2019-05-04 21:32:00 +02:00
committed by Ron Evans
parent 46d5ea8cf6
commit 9a54ee4241
9 changed files with 112 additions and 130 deletions
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compiler/channel.go
+26 -12
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@@ -12,13 +12,6 @@ import (
// emitMakeChan returns a new channel value for the given channel type.
func (c *Compiler) emitMakeChan(expr *ssa.MakeChan) (llvm.Value, error) {
valueType := c.getLLVMType(expr.Type().(*types.Chan).Elem())
if c.targetData.TypeAllocSize(valueType) > c.targetData.TypeAllocSize(c.intType) {
// Values bigger than int overflow the data part of the coroutine.
// TODO: make the coroutine data part big enough to hold these bigger
// values.
return llvm.Value{}, c.makeError(expr.Pos(), "todo: channel with values bigger than int")
}
chanType := c.mod.GetTypeByName("runtime.channel")
size := c.targetData.TypeAllocSize(chanType)
sizeValue := llvm.ConstInt(c.uintptrType, size, false)
@@ -30,14 +23,27 @@ func (c *Compiler) emitMakeChan(expr *ssa.MakeChan) (llvm.Value, error) {
// emitChanSend emits a pseudo chan send operation. It is lowered to the actual
// channel send operation during goroutine lowering.
func (c *Compiler) emitChanSend(frame *Frame, instr *ssa.Send) {
valueType := c.getLLVMType(instr.Chan.Type().(*types.Chan).Elem())
valueType := c.getLLVMType(instr.X.Type())
ch := c.getValue(frame, instr.Chan)
chanValue := c.getValue(frame, instr.X)
valueSize := llvm.ConstInt(c.uintptrType, c.targetData.TypeAllocSize(chanValue.Type()), false)
coroutine := c.createRuntimeCall("getCoroutine", nil, "")
// store value-to-send
c.builder.SetInsertPointBefore(coroutine.InstructionParent().Parent().EntryBasicBlock().FirstInstruction())
valueAlloca := c.builder.CreateAlloca(valueType, "chan.value")
c.builder.SetInsertPointBefore(coroutine)
c.builder.SetInsertPointAtEnd(coroutine.InstructionParent())
c.builder.CreateStore(chanValue, valueAlloca)
valueAllocaCast := c.builder.CreateBitCast(valueAlloca, c.i8ptrType, "chan.value.i8ptr")
c.createRuntimeCall("chanSendStub", []llvm.Value{llvm.Undef(c.i8ptrType), ch, valueAllocaCast, valueSize}, "")
// Do the send.
c.createRuntimeCall("chanSend", []llvm.Value{coroutine, ch, valueAllocaCast, valueSize}, "")
// Make sure CoroSplit includes the alloca in the coroutine frame.
// This is a bit dirty, but it works (at least in LLVM 8).
valueSizeI64 := llvm.ConstInt(c.ctx.Int64Type(), c.targetData.TypeAllocSize(chanValue.Type()), false)
c.builder.CreateCall(c.getLifetimeEndFunc(), []llvm.Value{valueSizeI64, valueAllocaCast}, "")
}
// emitChanRecv emits a pseudo chan receive operation. It is lowered to the
@@ -46,13 +52,21 @@ func (c *Compiler) emitChanRecv(frame *Frame, unop *ssa.UnOp) llvm.Value {
valueType := c.getLLVMType(unop.X.Type().(*types.Chan).Elem())
valueSize := llvm.ConstInt(c.uintptrType, c.targetData.TypeAllocSize(valueType), false)
ch := c.getValue(frame, unop.X)
coroutine := c.createRuntimeCall("getCoroutine", nil, "")
// Allocate memory to receive into.
c.builder.SetInsertPointBefore(coroutine.InstructionParent().Parent().EntryBasicBlock().FirstInstruction())
valueAlloca := c.builder.CreateAlloca(valueType, "chan.value")
c.builder.SetInsertPointBefore(coroutine)
c.builder.SetInsertPointAtEnd(coroutine.InstructionParent())
valueAllocaCast := c.builder.CreateBitCast(valueAlloca, c.i8ptrType, "chan.value.i8ptr")
valueOk := c.builder.CreateAlloca(c.ctx.Int1Type(), "chan.comma-ok.alloca")
c.createRuntimeCall("chanRecvStub", []llvm.Value{llvm.Undef(c.i8ptrType), ch, valueAllocaCast, valueOk, valueSize}, "")
// Do the receive.
c.createRuntimeCall("chanRecv", []llvm.Value{coroutine, ch, valueAllocaCast, valueSize}, "")
received := c.builder.CreateLoad(valueAlloca, "chan.received")
if unop.CommaOk {
commaOk := c.builder.CreateLoad(valueOk, "chan.comma-ok")
commaOk := c.createRuntimeCall("getTaskPromiseData", []llvm.Value{coroutine}, "chan.commaOk.wide")
commaOk = c.builder.CreateTrunc(commaOk, c.ctx.Int1Type(), "chan.commaOk")
tuple := llvm.Undef(c.ctx.StructType([]llvm.Type{valueType, c.ctx.Int1Type()}, false))
tuple = c.builder.CreateInsertValue(tuple, received, 0, "")
tuple = c.builder.CreateInsertValue(tuple, commaOk, 1, "")